Re: Optical system for Mark IV

[TASSmuto@subaru-soft.co.jp]

ALAIN MAURY wrote:
> ... ( any japanese amateur astronomer out there ? ).

(Hmmm, It's a great chance to post my first message to the TASS list :-)

>In the reputed lenses, which should be able to cover a 2K, or even
>a 4K chip is the Pentax SDUF II made for the Pentax 6x7. I know I'll
>buy one of these some days. They seem to be quite in use in Japan 
>among amateur astronomers. They also are quite expensive, I think
>in the $3,000 price range. Some amateurs are using them with small
>CCDs and say the images are good, but nobody knows on a large field.

I've heard that Pentax SDUF/SDUF-II is rather good on a "large" field -
some amateurs are using them with 4x5inch TechnicalPan film(=TP4415.)
The image plane is reasonablely flat (How to keep film sheet flat,
during exposure, is another matter, I guess) and you get image circle
dia. over 100mm...(if you are ok with some vignetting.)

>One thing I have read about in a japanese amateur astronomy magazine
>called interactive astronomy ...is what seem to be a modification of a
>regular C8 to a Schmidt telescope.

I think the issue you referring to is vol.11(Autumn 1997.)
There are two plans based on Celestron/Meade SCT: (1) "Coma-less Cassegrain"
configuration(*) and (2) "pure" Schmidt camera.  "Retrofit" kits will be 
available from Tenmon-Guide, according to the article.

(*)By the way, Takahashi is developing such Baker Schmidt "camera." 
(A coma-free flat-field variant of Schmidt Cassegrain telescope, I thought.)
				Nozomu Muto
-- 
Nozomu Muto(Mr.) c/o Subaru Software Inc.
1-2-1-902 Sinjuku, Sinjuku, Tokyo 160, Japan
FAX: +81/3-3356-0274, EMAIL: muto@subaru-soft.co.jp